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    <meta charset="UTF-8">
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    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
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<body>
    <script>
        // 1.转换成字符串类型
        var num = 18;
        var str = num.toString()
        console.log(str);
        // 2.string()
        console.log(String(num));
        // 3.利用+拼接
        console.log(num + '');
    </script>
</body>

</html>